Effect of solvent evaporation technique on the characteristics of curing agent microcapsules and the curing process

Abstract In this work, diuron (DCMU), which was encapsulated using polystyrene (PS) as the shell material via solvent evaporation method in an oil-in-water emulsion was used as an accelerator. Due to their temperature control release performance, these microcapsule-type latent curing agents have an excellent impact on prolonging the shelf life of prepreg in a one-component system. The structure and properties of microcapsules, such as size and coating rate, were influenced by dispersed phase/continuous phase ratio, mass ratio of core/shell, emulsifier concentration, and agitation rate. Orthogonal array design experiments were used to obtain optimum synthetic parameters. The temperature controlled release performance of microcapsules plays an important role during the curing reaction. Furthermore, the released amount of the curing agent throughout the heating process was evaluated. With the increase in the heating rate, the release rate of the core materials showed a growing trend. To explore the influence of the microcapsule-type curing agent by non-isothermal differential scanning calorimetry (DSC) technique at different heating rates, the heating flow of microcapsule-type and normal-type curing agents in the curing process were tested and data were compared., Compared to the normal ones, the microcapsule curing agents exhibited delayed kinetic behaviors throughout the curing process. The variations of activation energy over the course of the reaction were evaluated by using Iso-conversional methods. The results indicated that the activation energy of the microcapsule-type curing agent indicated a continuous decrease, proving that it is easier for the reaction to carry through to completion.